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448
AGPN40 KWNM 102159
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
159 PM PST SAT DEC 10 2016

.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Pacific N of 30N and E of 150W.

A broad upper trough is over the waters from the PZ5 waters
northwest and west...containing a series of ebedded shortwaves.
18Z surface analysis shows several lows between 49N and 52N with
the strongest of these just north of the PZ5 waters. Both ASCAT
passes from around 18Z miss the area of strongest westerly
gradient over the Washington waters. With negative static
stabilities still prevailing over the area north of a cold front
over the north-central PZ6 waters...as was previously the
case...populated wind grids with the 12Z GFS boosting the boundary
layer winds toward the higher first sigma layer winds in the
colder air north of the front and to the south of the front where
conditions are more neutrally stable the grids are close to the
GFS 10m winds. In the ASCAT imagery winds are 20 kt or less over
the PZ6 waters...highest near the front...over the far north and
also in the far southeast near Guadalupe Island...with high
pressure ridge dominant south of front front. With moderate
confidence the tonight forecast will start with marginal gales
over the northernmost two zones.

12Z models are in good agreement through Monday night weakening
the main low near Vancouver Island Sunday with other weaker lows
folowing in the cyclonic westerly flow Sunday into Monday night.
Upper low dropping south from southeast Alaska will likely trigger
a new low near the Queen Charlottes Sunday night which will then
drop southeast and dissipate near the Oregon coast Monday night as
an inverted trough forms over the PZ5 area. Upper air patttern
evolves as a series of shortwaves drop south to the west of the
waters and carve out a deepening upper trough over or just west of
the waters through the remiander of the period. This will pick up
a series of southern stream waves along a nearly stationary
frontal boundary west of California but since the shortwaves
maintain positive tilt will not expect any of the lows to develop
gales as they enter the central PZ6 area. The first wave Tuesday
and Tuesday night has best model agreement. Hence populated with
the representative 12Z GFS through Tuesday night. There is greater
model spread for the second wave and therefore used the 12Z
ECMWF compromise solution Wednesday and Wednesday night while GFS
is stronger and develops marginal gale-force boundary layer winds.
After that models build a ridge west of the waters placing all the
waters in northwest flow. Used 12Z GFS 10m winds for Thursday and
Thursday night with areas of strongest winds 30 kt while 12Z ECMWF
brings winds up close to gale in the northwest waters.

Seas...Populateed wave grids with representative 12Z ECMWF WAM for
tonight before blending with 12Z ENP WW3 through Tuesday night and
after that 12Z ECMWF WAM.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.

.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
.PZZ800...Inner Waters from Cape Flattery to Cape Shoalwater...
     Gale tonight.
.PZZ900...Outer Waters from Cape Flattery to Cape Shoalwater...
     Gale tonight.

.PZ6 California Waters...
     None.

$$

.Forecaster Bancroft. Ocean Prediction Center.



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